The present invention relates to vertical take-off and landing (VTOL) aircraft and more specifically to a pulsejet vertical propulsion system for a VTOL aircraft.
Vertical takeoff and landing (VTOL) aircraft are known. A variety of methods have been employed to provide vertical takeoff capability. These methods include: providing ducts to redirect the discharge from the main propulsion unit of the aircraft in a downward direction to provide vertical lift; providing a tilt mechanism to permit the main engine(s) of the aircraft to tilt and provide vertical thrust; and providing separate engines for driving fan systems to lift the aircraft. In each of the known concepts, additional components and structure are added to provide vertical thrust required for vertical takeoff. The complexity of the aircraft increases greatly when the design is modified to use an existing main engine for vertical thrust. Aircraft range and payload capabilities are reduced when weight and structural changes required to incorporate vertical takeoff engines are incorporated into an aircraft.
When an aircraft is optimized for horizontal flight, adding the capability of vertical takeoff and landing decreases its horizontal flight capabilities, i.e., speed, range and payload. If an aircraft is optimized for hovering and vertical lift capability, high speed horizontal flight capability or long range are usually lost. The complexity of an aircraft designed to accommodate both horizontal and VTOL capabilities also increases the maintenance requirements on the aircraft and therefore increases the overall life cycle costs to operate the aircraft.
Jet engine aircraft capable of VTOL flight have a normally restricted area of operation. This restriction results from the high velocity and high temperature exhaust gases exiting from the jet engine(s) which are vectored to provide VTOL capability. The high temperature and pressure gases require that special landing areas with hardened landing surfaces be provided, i.e., a concrete landing pad or a steel plate landing surface. The special landing areas prevent damage to surrounding area, negatively impacting the surface pitch of the landing area, and minimize the chance of ingesting material into the jet engine(s). Attempting to land VTOL jet or propeller powered aircraft over non-hardened surfaces can result in a conflagration of ground or vegetation material being expelled into the atmosphere about the aircraft engines which can be entrained into the inlets of the engine causing engine damage and/or failure.
A need therefore exists for a VTOL aircraft wherein a vertical lift capability is provided which is distinct from the normal horizontal flight engine(s). A need also exists for an engine design providing vertical lift capability which exhausts at both a reduced temperature and pressure and provides a significantly simplified, durable engine design which allows a multitude of vertical lift engines to be provided for redundancy, while providing engines less susceptible to damage from ingestion of ground debris.
According to a preferred embodiment of the present invention, a vertical takeoff and landing (VTOL) aircraft provides separate axial and vertical propulsion sources including at least one pulsejet engine for vertical propulsion.
According to one preferred embodiment, each pulsejet engine is provided in a separate augmentor bay. The augmentor bay includes an inner and outer wall provided to support the pulsejet engine, and a pair of apertured sidewalls. The apertures in the sidewalls provide for equalization flow between discharges of adjacent pulsejet engines. Equalizing the discharge from each of the pulsejet engines allows the thrust to be balanced across a bank of pulsejet engines. Therefore, if an individual pulsejet engine is operating above or below a desired operating condition, the resultant thrust from the individual pulsejet engine is balanced with the bank of pulsejet engines and its non-conforming condition does not jeopardize the aircraft.
The structure of the pulsejet engine of the present invention is integrated into the structure of the aircraft such that the structural loads of the aircraft are partially carried by the pulsejet and ejector engine structure. This reduces the overall weight impact on the aircraft due to addition of the pulsejet engines because separate mounting structure to support each of the pulsejet engines is not required. The pulsejet engines arranged in banks of engines are throttled using a fuel injection system, or the thrust from each individual pulsejet or bank of pulsejets can be controlled using one or more deflection plates. The deflection plates can be provided as rotatable cowls which are provided on both an inlet port of each augmentor bay and a discharge port of each augmentor bay. As known in the art, each augmentor bay provides tapered walls acting as an ejector for each pulsejet engine, thereby increasing the thrust-to-weight ratio of each pulsejet engine.
The inlet cowl isolates the entrance to each pulsejet engine bay therefore allowing the bay to be isolated from ambient conditions and prevent debris and undesirable materials from entering the pulsejet engines when the engines are shut down. The outlet cowl for the exhaust augmentor bays is provided to assist in controlling pulsejet engine thrust. The outlet cowl can be rotatably positioned ranging from fully opened to fully closed positions such that individual or groups of augmentor bays can be completely opened or partially isolated controlling vertical thrust of the aircraft, or completely isolated to prevent debris and undesirable material from entering the pulsejet engines when the engines are shut down.
The use of banks of individual pulsejet engines for vertical lift and the main engine(s) for horizontal thrust of the aircraft provides the capability of optimizing both the main engine and the VTOL engines of the aircraft. Either subsonic or supersonic speeds for an aircraft can therefore be provided because the VTOL pulsejet engine banks are isolated after vertical flight is achieved.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.